The formula for kinetic energy in generic terms is KE = 1/2 * (mass) * (velocity)^2, or 1/2 times the mass times the velocity squared. Reduced with all the proper conversion factors, it is KineticEnergy = .5 * weight * velocity^2 / 7000 / 32.175

Here's a good website:

Bullet Kinetic Energy Calculator
So as it works out, your .30-30 has a KE at the muzzle of 1826ft-lbs, and your smokepole has a KE at the muzzle of 1122 ft-lbs. That being said, the roundball also has a "large slow moving punch" factor that makes it a good game-getter.